As the final season of "The Sopranos" progressed and the bodies kept piling up, it became clearer than ever that Tony, the head of a New Jersey crime family played by James Gandolfini, wouldn't have a happy ending to his story in the 2007 finale, "Made in America."
Audiences didn't expect the show's final scene to be the Soprano family meeting at a diner while "Don't Stop Believin'" played on a jukebox. The camera showed the front door of the diner opening before cutting to black, ending the show.
People across the country thought HBO had crashed. But the show's creator, David Chase, made it clear that this was the end and that he had no intention of telling us whether the person who arrived at the diner was there to whack Tony.
By the time season five of "Game of Thrones" was airing in 2015, audiences knew not to get attached to anyone.
But if "Thrones" had a main character by season five, it was Jon, played by Kit Harington.
So when the season concluded with the episode "Mother's Mercy," in which his so-called brothers conspired to kill him via group stabbing, fans were shocked — well, the ones who hadn't read the books at least.
After the season ended, Harington swore he wasn't returning to the world of Westeros, which made viewers wonder: What would happen next? You'd have to tune in to season six to find out.
"Star Trek" is a fairly episodic show by design. But when the season-three finale aired in June 1990, it became clear that even "Star Trek" knew the power of a good cliffhanger.
The third season ended with the episode "The Best of Both Worlds," in which Jean-Luc Picard (Patrick Stewart), the brave captain of the Enterprise, is taken captive by an evil alien species called the Borg, who have the power to eventually take over the galaxy.
Picard's friend and first officer, William Riker (Jonathan Frakes), is left with a choice: Does he mount a rescue mission or take the opportunity to wipe out the Borg, Picard included?
The episode concludes with Riker firing on the Borg's ship before hitting us with a "To be continued…" leaving Picard's fate up in the air until season four.
From the first episode of "Lost," it was clear each episode would split the action between present-day happenings on the island and flashbacks, usually focused on one survivor.
But the season-three finale, "Through the Looking Glass," which aired in 2007, seemed different. We watched as Jack became heavily depressed, even suicidal, and hooked on painkillers — a previously unknown part of Jack's history.
But the last scene of the finale showed us that this wasn't a flashback but a flash-forward, letting us know that at least Jack and Kate (Evangeline Lilly) would be rescued from the island at some point and that Jack would tearfully tell Kate they had to go back to the island, changing the course of "Lost" forever.
By the time "Dallas" entered its third season, audiences were captivated by the wheeling and dealing of the Ewing oil/cattle dynasty.
And no character was more admired (or reviled) than J.R. Ewing (Larry Hagman), a scheming oil tycoon who stopped at nothing to get what he wanted.
When the season-three finale, "A House Divided," concluded with his shooting by a mysterious gunman, TV audiences became consumed by the question "Who shot J.R.?"
It could've been anyone, as everyone on the show had a reason to kill J.R. In fact, everyone on the show was filmed shooting J.R. to keep it a secret from audiences and the crew alike.
It took four episodes of season four before the shooter's identity was revealed.
This wasn't a season finale, but it was still very nerve-racking to wait a week to see if President Fitzgerald Grant III, played by Tony Goldwyn, had survived getting shot while entering his birthday party.
The season two episode, "Defiance," was wild enough without the attempt; it was mainly about James, a reporter, investigating the claim that the voting machines had been rigged in the election that resulted in Fitz's win.
But then, in the last two minutes — bang. Fitz was shot by an unseen assailant, thrown back into his limo, and rushed to the hospital, his fate unknown.
The next episode, "Happy Birthday, Mr. President," revealed that Fitz was alive, but he wouldn't wake up for a few more episodes. Classic "Scandal" drama.
Season one of "Grey's Anatomy," which aired in 2005, had a lot of characters to juggle, but perhaps the most compelling plot line at the time was watching Meredith Grey (Ellen Pompeo), a surgical intern, fall in love with her boss, the neurosurgeon Derek Shepherd (Patrick Dempsey).
It seemed they'd finally figured out their issues in the finale of season one, "Who's Zoomin' Who?" — only for a statuesque redhead (Kate Walsh) to greet Derek and say to Meredith, "You must be the woman who's been screwing my husband."
Around the country, jaws dropped. Answers would come months later, in season two.
Ross (David Schwimmer) and Rachel (Jennifer Aniston) were one of the greatest will-they-won't-they couples of our time.
It was a huge surprise when Ross decided to marry Emily (Helen Baxendale), his British girlfriend of only a few months, in the 1998 finale of season four, "The One With Ross's Wedding."
But the pull of Ross and Rachel's unfinished business was too strong for Ross, and viewers (and Rachel) gasped as Ross said, "I, Ross, take thee, Rachel" at the altar.
The officiant asks Emily if he should continue. Before we find out her answer, the episode ends, leaving Ross' marital status up in the air until the season-five premiere, aptly titled "The One After Ross Says Rachel."
"How I Met Your Mother" frequently employed cliffhangers — in fact, the whole show could be considered a cliffhanger, as Ted didn't meet the titular mother until the series finale.
But one of the longest-running cliffhangers was first hinted at in the premiere of season six, when the gang was seen in the near future attending a wedding where Ted was the best man — but fans didn't get a glimpse at the bride or the groom.
That is, until the season finale when it was finally revealed that the groom was notorious womanizer and commitment phobe Barney Stinson (Neil Patrick Harris).
But who was the bride?
We had to wait an entire season until the finale of season seven, when it was finally revealed that Barney would eventually marry Robin.
And then they lived happily ever after, as long as you ignore the events of the controversial series finale.
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